Chiao Cheng | 89437e8 | 2012-11-01 13:41:51 -0700 | [diff] [blame] | 1 | /* |
| 2 | * Copyright (C) 2010 The Android Open Source Project |
| 3 | * |
| 4 | * Licensed under the Apache License, Version 2.0 (the "License"); |
| 5 | * you may not use this file except in compliance with the License. |
| 6 | * You may obtain a copy of the License at |
| 7 | * |
| 8 | * http://www.apache.org/licenses/LICENSE-2.0 |
| 9 | * |
| 10 | * Unless required by applicable law or agreed to in writing, software |
| 11 | * distributed under the License is distributed on an "AS IS" BASIS, |
| 12 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 13 | * See the License for the specific language governing permissions and |
| 14 | * limitations under the License. |
| 15 | */ |
| 16 | |
Gary Mai | 69c182a | 2016-12-05 13:07:03 -0800 | [diff] [blame] | 17 | package com.android.contacts.list; |
Chiao Cheng | 89437e8 | 2012-11-01 13:41:51 -0700 | [diff] [blame] | 18 | |
| 19 | import android.content.Context; |
Phil Weaver | 80fc409 | 2016-11-02 12:31:43 -0700 | [diff] [blame] | 20 | import android.os.Build; |
Chiao Cheng | 89437e8 | 2012-11-01 13:41:51 -0700 | [diff] [blame] | 21 | import android.util.AttributeSet; |
| 22 | import android.widget.ListView; |
| 23 | |
| 24 | /** |
| 25 | * A ListView that can be asked to scroll (smoothly or otherwise) to a specific |
| 26 | * position. This class takes advantage of similar functionality that exists |
| 27 | * in {@link ListView} and enhances it. |
| 28 | */ |
| 29 | public class AutoScrollListView extends ListView { |
| 30 | |
| 31 | /** |
| 32 | * Position the element at about 1/3 of the list height |
| 33 | */ |
| 34 | private static final float PREFERRED_SELECTION_OFFSET_FROM_TOP = 0.33f; |
| 35 | |
| 36 | private int mRequestedScrollPosition = -1; |
| 37 | private boolean mSmoothScrollRequested; |
| 38 | |
| 39 | public AutoScrollListView(Context context) { |
| 40 | super(context); |
| 41 | } |
| 42 | |
| 43 | public AutoScrollListView(Context context, AttributeSet attrs) { |
| 44 | super(context, attrs); |
| 45 | } |
| 46 | |
| 47 | public AutoScrollListView(Context context, AttributeSet attrs, int defStyle) { |
| 48 | super(context, attrs, defStyle); |
| 49 | } |
| 50 | |
| 51 | /** |
| 52 | * Brings the specified position to view by optionally performing a jump-scroll maneuver: |
| 53 | * first it jumps to some position near the one requested and then does a smooth |
| 54 | * scroll to the requested position. This creates an impression of full smooth |
| 55 | * scrolling without actually traversing the entire list. If smooth scrolling is |
| 56 | * not requested, instantly positions the requested item at a preferred offset. |
| 57 | */ |
| 58 | public void requestPositionToScreen(int position, boolean smoothScroll) { |
| 59 | mRequestedScrollPosition = position; |
| 60 | mSmoothScrollRequested = smoothScroll; |
| 61 | requestLayout(); |
| 62 | } |
| 63 | |
| 64 | @Override |
| 65 | protected void layoutChildren() { |
| 66 | super.layoutChildren(); |
| 67 | if (mRequestedScrollPosition == -1) { |
| 68 | return; |
| 69 | } |
| 70 | |
| 71 | final int position = mRequestedScrollPosition; |
| 72 | mRequestedScrollPosition = -1; |
| 73 | |
| 74 | int firstPosition = getFirstVisiblePosition() + 1; |
| 75 | int lastPosition = getLastVisiblePosition(); |
| 76 | if (position >= firstPosition && position <= lastPosition) { |
| 77 | return; // Already on screen |
| 78 | } |
| 79 | |
| 80 | final int offset = (int) (getHeight() * PREFERRED_SELECTION_OFFSET_FROM_TOP); |
| 81 | if (!mSmoothScrollRequested) { |
| 82 | setSelectionFromTop(position, offset); |
| 83 | |
| 84 | // Since we have changed the scrolling position, we need to redo child layout |
| 85 | // Calling "requestLayout" in the middle of a layout pass has no effect, |
| 86 | // so we call layoutChildren explicitly |
| 87 | super.layoutChildren(); |
| 88 | |
| 89 | } else { |
| 90 | // We will first position the list a couple of screens before or after |
| 91 | // the new selection and then scroll smoothly to it. |
| 92 | int twoScreens = (lastPosition - firstPosition) * 2; |
| 93 | int preliminaryPosition; |
| 94 | if (position < firstPosition) { |
| 95 | preliminaryPosition = position + twoScreens; |
| 96 | if (preliminaryPosition >= getCount()) { |
| 97 | preliminaryPosition = getCount() - 1; |
| 98 | } |
| 99 | if (preliminaryPosition < firstPosition) { |
| 100 | setSelection(preliminaryPosition); |
| 101 | super.layoutChildren(); |
| 102 | } |
| 103 | } else { |
| 104 | preliminaryPosition = position - twoScreens; |
| 105 | if (preliminaryPosition < 0) { |
| 106 | preliminaryPosition = 0; |
| 107 | } |
| 108 | if (preliminaryPosition > lastPosition) { |
| 109 | setSelection(preliminaryPosition); |
| 110 | super.layoutChildren(); |
| 111 | } |
| 112 | } |
| 113 | |
| 114 | |
| 115 | smoothScrollToPositionFromTop(position, offset); |
| 116 | } |
| 117 | } |
Phil Weaver | 80fc409 | 2016-11-02 12:31:43 -0700 | [diff] [blame] | 118 | |
| 119 | @Override |
| 120 | protected void onLayout(boolean changed, int l, int t, int r, int b) { |
| 121 | super.onLayout(changed, l, t, r, b); |
| 122 | |
| 123 | // Workaround for b/31160338. |
| 124 | if (android.os.Build.VERSION.SDK_INT == Build.VERSION_CODES.N |
| 125 | || android.os.Build.VERSION.SDK_INT == Build.VERSION_CODES.N_MR1) { |
| 126 | layoutChildren(); |
| 127 | } |
| 128 | } |
Chiao Cheng | 89437e8 | 2012-11-01 13:41:51 -0700 | [diff] [blame] | 129 | } |